Make `cargo-platform` optional #190

	name: CI
	on: [push, pull_request]

	jobs:
	rustfmt:
	name: rustfmt
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- name: Install rust
	run: rustup update --no-self-update stable && rustup default stable
	- name: Check formatting
	run: cargo fmt -- --check

	clippy:
	name: clippy
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- name: Install rust
	run: rustup update --no-self-update stable && rustup default stable
	- name: Clippy check
	run: cargo clippy --all-features -- -Dwarnings

	test:
	name: Test
	runs-on: ubuntu-latest
	strategy:
	matrix:
	include:
	- rust: stable
	- rust: beta
	- rust: nightly
	- rust: 1.73.0
	steps:
	- uses: actions/checkout@v2
	- name: Install rust
	run: rustup update --no-self-update ${{ matrix.rust }} && rustup default ${{ matrix.rust }}
	- name: Run tests
	run: \|
	cargo build --verbose
	cargo build --verbose --no-default-features
	cargo test --verbose
	cargo test --verbose --no-default-features
	cargo test --verbose --all-features

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